There are certain situations where a crop delivers higher resolution than a FF with the same lens (even disregarding DoF, AF and the corners). Roger M. Clark has nice shots of the moon with the 5D2 and the 7D that show this:

When I wrote, "All else being equal, the larger the format, the better the image quality," there was obviously a bit of shorthand going on. Particularly, to maintain the same field of view with a larger format, you need a longer focal length. Just as you wouldn't compare a P&S with an 8mm lens to a 5DIII with an 8mm lens, you really can't compare a 7D with a 300mm lens to a 5DIII with a 300mm lens -- even if you can physically mount the same lens to both cameras. Rather, you'd compare that P&S with an 8mm lens to a 5DIII with a 50mm lens, and you should compare the 7D with a 300mm lens to a 5DIII with a 500mm lens -- native, in all cases, not with extenders.

And you will, indeed, get substantially better images (with comparable framing) from a 5DIII with a 500mm lens than a 7D with a 300mm lens. That an uncropped image from a 7D with a 300mm lens is superior to a cropped image with a 300mm lens is no more surprising than that slicing away all of an 8x10 negative shot with a 300mm lens but for a 1" x 1.5" rectangle results in a worse image than you'd get from a 135 frame with a 35mm lens.

Once again, all else is clearly not always equal. If all you've got is a 300mm lens and you want to shoot the full disc of the moon, yes, of course, you're going to get better results from that lens with a 7D than a 5DIII. But the guy next to you with a 5DIII and a 1200mm f/5.6 is going to get an image of the moon that puts yours with your 7D to shame. And the guy the next hill over, the one with a 32" Dobsonian? Well....

I didn't look at the tests done, as I've been using cropped sensor cameras since 2003 and full frame (& APS-H) cameras since 2007 and can say that generally, the bigger the sensor the better the overall quality of the image. It's not to say that a given combination of APS-C camera with a given lens in a certain situation won't out perform a full frame with a particular lens in the same situation, but in more situations than not you'll probably get the best results from the larger sensor camera. That's why they are still making large sensor cameras, if that wasn't true then the 4/3rds format would have taken over the industry years ago.

This reminds me a little of the comparisons between medium format and 35mm film. Back in the day I shot both, had a Rolleicord that may have had a focusing problem, always gave me just slightly soft images. I could get better images with my Canon AE-1 using Technical Pan film, ASA (same as ISO) 25, which had super tight grain that could be enlarged up to 16x20 without seeing the grain for the most part. Did that mean that 35mm film cameras were better than medium format? Of course not.

At Building Panoramics we recently purchased a 650D as a family camera for my partner. When it arrived we thought it would be interesting to test it against our 5D mk1 and mk2s. Our test was wholly empirical - we shot both cameras at ISO 100, from a sturdy tripod, and used a 50mm 1.4 on the 650 and an 85mm 1.8 on the MK2, both at f8 as this is the aperture we tend to use for buildings. We expected to see a difference.

The first two pictures attached are the whole images, reduced for the web. The third and fourth are the 100% crops.

We could not tell any difference, apart from the DoF. This surprised us as the mk2 was about £2000 when we bought it in 2008, and the 650 cost about a third of that.

So we took the 650D out on assignment with the FFs, and I can say that there is something about the images from the 650 that does not quite have the quality of the 5Ds. Just what this is is difficult to quantify: maybe it's the subtlety of the tonal graduation in difficult areas, I don't know. I don't think there is any difference in the actual sharpness.

Most tests are done at close distances, and as East Wind Photography has suggested, the goal posts move in practical applications where greater distances are involved.

Once again, all else is clearly not always equal. If all you've got is a 300mm lens and you want to shoot the full disc of the moon, yes, of course, you're going to get better results from that lens with a 7D than a 5DIII. But the guy next to you with a 5DIII and a 1200mm f/5.6 is going to get an image of the moon that puts yours with your 7D to shame.

Once again, all else is clearly not always equal. If all you've got is a 300mm lens and you want to shoot the full disc of the moon, yes, of course, you're going to get better results from that lens with a 7D than a 5DIII. But the guy next to you with a 5DIII and a 1200mm f/5.6 is going to get an image of the moon that puts yours with your 7D to shame. And the guy the next hill over, the one with a 32" Dobsonian? Well....

yeah..... but is the guy on the last hill hand-holding the 32" Dobsinian? And if he is, who's going to argue with him?

Once again, all else is clearly not always equal. If all you've got is a 300mm lens and you want to shoot the full disc of the moon, yes, of course, you're going to get better results from that lens with a 7D than a 5DIII. But the guy next to you with a 5DIII and a 1200mm f/5.6 is going to get an image of the moon that puts yours with your 7D to shame. And the guy the next hill over, the one with a 32" Dobsonian? Well....

yeah..... but is the guy on the last hill hand-holding the 32" Dobsinian? And if he is, who's going to argue with him?

The <a href="http://hubblesite.org/">gang down south</a> might be able to give him a good run for the money....

Let us say that you have a APS sensor 24Mp with the same S/N as a 24Mp 24x36 sensor then it is an optical question, it is hard to make a APS lens 1,5 1,6 times better which is require compared to 24x36mm lens.

This is incorrect.

Because there will be less absolute magnification for a same-sized print with the larger format, even if the sensors have the same pixel dimensions, the larger format will be sharper and have less noise. Again, always assuming all else is comparable, including a longer focal length lens for the larger format.

Let us say that you have a APS sensor 24Mp with the same S/N as a 24Mp 24x36 sensor then it is an optical question, it is hard to make a APS lens 1,5 1,6 times better which is require compared to 24x36mm lens.

This is incorrect.

Because there will be less absolute magnification for a same-sized print with the larger format, even if the sensors have the same pixel dimensions, the larger format will be sharper and have less noise. Again, always assuming all else is comparable, including a longer focal length lens for the larger format.

Cheers,

b&

Assuming M.R. means signal to noise ratio by S/N, then he is correct. Actually, the linear resolving power of the lens needs to be increased by the crop factor, and the absolute resolving power of the lens needs to be increased by the square of the crop factor. But this is all based on an imaginary hypothesis, an APS sensor with the exact same S/N ratio as full-frame. Anything is true if the hypothesis itself is false.

Let us say that you have a APS sensor 24Mp with the same S/N as a 24Mp 24x36 sensor then it is an optical question, it is hard to make a APS lens 1,5 1,6 times better which is require compared to 24x36mm lens.

This is incorrect.

Because there will be less absolute magnification for a same-sized print with the larger format, even if the sensors have the same pixel dimensions, the larger format will be sharper and have less noise. Again, always assuming all else is comparable, including a longer focal length lens for the larger format.

Cheers,

b&

is it, if the S/N and Mp is the same from the two sensor areas, then it must be an optical question , and there the APS lenses must be 1,5 1.6 better than the 24x36mm lens.

As I already explained, it is a question of how much enlargement is necessary for a print.

If you're making a 24" x 36" print, the APS-C image will be enlarged 41x from the sensor's original size of 14.8mm x 22.2 mm, but the full-frame will only be enlarged 25x from the sensor's original size of 24mm x 36mm.

Whether you measure S/N in noise per pixel or noise per square mm of sensor, because you've got two and a half times as many square mm of sensor per pixel with the larger format, you're getting that much better of an overall signal to noise ratio.

Imagine you were back in the days of film. You have a 35mm camera loaded with Velveeta on one tripod and an 8x10 view camera loaded with the exact same film on a second tripod. The 35mm camera has a 50mm lens and the view camera has a 400mm lens, both of which give the same normal field of view on the respective cameras.

You'd agree that, since it's the exact same film, the exact same chemistry, that the S/N ratio is exactly the same, right?

Now, let's say we're making an 8" x 10" print from the exposure. The 35mm negative needs to get enlarged 7.5x to make the print, but, for the view camera, it's a contact print.

If you don't agree that the contact print from the view camera will be dramatically sharper and have far less grain than the enlargement from the 35mm camera, then you truly are hopeless.

Now, you might still argue that the pixel dimensions are relevant, but I'll show they're not.

Let's not use traditional printing methods, but rather scan the film. But we want to wind up with the same megapickle files for both, to simulate this contrived example. We're going to scan the 8x10 negate at a lowly 300 ppi, and we're going to scan the 35mm negative at a whopping 2250 ppi. We're still going to make an 8x10 print, and we're going to do it at 300 ppi. And, because of the resolutions I picked, it "just happens" that no interpolation of either file is necessary; both will still print at 300 ppi at 8" x 10".

Once again, if you still don't think that the print from the 300 ppi scan of the view camera's negative will blow away the 2250 ppi scan from the 35mm camera, you're hopeless.

This assumes that you also always print the full frame. For some cropping is always required. If you crop the same image to the same composition your results may vary. We don't always have the luxury of filling the frame especially when using a prime lens in less than adequate quarters.

Let us say that you have a APS sensor 24Mp with the same S/N as a 24Mp 24x36 sensor then it is an optical question, it is hard to make a APS lens 1,5 1,6 times better which is require compared to 24x36mm lens.

This is incorrect.

Because there will be less absolute magnification for a same-sized print with the larger format, even if the sensors have the same pixel dimensions, the larger format will be sharper and have less noise. Again, always assuming all else is comparable, including a longer focal length lens for the larger format.

Cheers,

b&

is it, if the S/N and Mp is the same from the two sensor areas, then it must be an optical question , and there the APS lenses must be 1,5 1.6 better than the 24x36mm lens.

As I already explained, it is a question of how much enlargement is necessary for a print.

If you're making a 24" x 36" print, the APS-C image will be enlarged 41x from the sensor's original size of 14.8mm x 22.2 mm, but the full-frame will only be enlarged 25x from the sensor's original size of 24mm x 36mm.

Whether you measure S/N in noise per pixel or noise per square mm of sensor, because you've got two and a half times as many square mm of sensor per pixel with the larger format, you're getting that much better of an overall signal to noise ratio.

Imagine you were back in the days of film. You have a 35mm camera loaded with Velveeta on one tripod and an 8x10 view camera loaded with the exact same film on a second tripod. The 35mm camera has a 50mm lens and the view camera has a 400mm lens, both of which give the same normal field of view on the respective cameras.

You'd agree that, since it's the exact same film, the exact same chemistry, that the S/N ratio is exactly the same, right?

Now, let's say we're making an 8" x 10" print from the exposure. The 35mm negative needs to get enlarged 7.5x to make the print, but, for the view camera, it's a contact print.

If you don't agree that the contact print from the view camera will be dramatically sharper and have far less grain than the enlargement from the 35mm camera, then you truly are hopeless.

Now, you might still argue that the pixel dimensions are relevant, but I'll show they're not.

Let's not use traditional printing methods, but rather scan the film. But we want to wind up with the same megapickle files for both, to simulate this contrived example. We're going to scan the 8x10 negate at a lowly 300 ppi, and we're going to scan the 35mm negative at a whopping 2250 ppi. We're still going to make an 8x10 print, and we're going to do it at 300 ppi. And, because of the resolutions I picked, it "just happens" that no interpolation of either file is necessary; both will still print at 300 ppi at 8" x 10".

Once again, if you still don't think that the print from the 300 ppi scan of the view camera's negative will blow away the 2250 ppi scan from the 35mm camera, you're hopeless.

This assumes that you also always print the full frame. For some cropping is always required. If you crop the same image to the same composition your results may vary. We don't always have the luxury of filling the frame especially when using a prime lens in less than adequate quarters.

If you're shooting side-by-side with a 7D and a 20mm prime, a 5DIII and a 35mm prime, and an 8x10 view camera and a 250mm prime, you're going to be cropping away the same proportional amount to get the same composition from each, rendering the cropping point moot.

If you're distance-limited, sure, it can make a difference...but generally not at much as most people tend to think. If that little birdie only fills an eighth of your frame with the 800mm f/5.6 on the 5DIII, you'll get better results putting the lens on the 7D, but not hugely better. The real answer is to improve your tracking skills so you can get closer and fill the frame, with whatever camera / lens combination.